Material treating method and apparatus



Dec. 21, 1965 J. J. FRANKLIN ETAL 3,224,452

MATERIAL TREATING METHOD AND APPARATUS Filed Oct. 16, 1965 5 Sheets-Sheet 1 A mvENToRs:

JOHN J. FRANKLlN EDWIN W. HINE II BY www All-TVSV im um m. m Lw i| l- :il a |-..w..,.,. A w n :EME: y

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Dec. 21, 1965 J. J. FRANKLIN ETAL 3,224,452

MATERIAL TREATING METHOD AND APPARATUS 5 Sheets-Sheet 2 Filed 0G11. 16, 1963 FIGB INVENTORSI JOHN J. FRANKLIN EDWIN w. HINE 1I ATTYS.

Dec. 21, 1965 J. J. FRANKLIN ETAI. 3,224,452

MATERIAL TREATING METHOD AND APPARATUS Filed oet. 16,' 1965 5 Sheets-Sheet 5 I- ICSl 4.

INVENTORS:

JOHN J. FRANKLIN EDWIN W. HINE. 1I

ATTYS.

United States Patent Oiice 3,224,452 Patented Dec. 21, 1965 3,224,452 MATERIAL TREA'IING METHOD AND APPARATUS John J. Franklin, Glenside, and Edwin W. Hine II, Philadelphia, Pa., assignors to Proctor & Schwartz, Inc., Philadelphia, Pa., a corporation of Pennsylvania Filed Oct. 16, 1963, Ser. No. 316,577 5 Claims. (Cl. 131-140) This invention relates to method and apparatus for treating materials, for example, such as tobacco.

In the course of making tobacco for cigarettes, cigars, etc., the tobacco leaves are stored for ageing for a period of from one to four years. In preparing the tobacco leaves for storage, the leaves are usually processed in a treating apparatus conventionally compising an elongated generally enclosed housing which is subdivided by partitions or curtains into zones or sections including a drying zone wherein a heated drying medium is circulated through the tobacco leaves to dry them to a very low moisture content, a cooling zone wherein a predetermined amount of heat is removed from the tobacco and an ordering zone where a predetermined controlled amount of moisture is added to the tobacco. A conventional conveyor transports the tobacco through the various zones of the apparatus, the partitions having openings therein to accommodate the conveyor. It is important to control very closely treating conditions in each zone of the apparatus to insure a processed material having a desired uniform condition to preclude damage thereof while in storage. For example, if all or portions of the tobacco are underdried or too wet, the excess moisture will cause mold or rot and sometimes damage due to spontaneous combustion. On the other hand, if the tobacco is overdried, damage also occurs.

In apparatus lof the above type, it has been found that it is dfiicult to achieve a predetermined uniform condition of the processed material even though the initial temperature of the medium circulated through the drying and cooling zones is controlled accurately and the amount of moisture added in the ordering zone is controlled closely. One of the major reasons for lack of uniformity is that in the cooling zone where fans are usually used to circulate fresh air through the material, there tends to be a lower air pressure over the bed of material than in the adjacent drying and ordering zones where the pressures are usually about equal. Thus, even though the cooling zone is separated from the ordering and drying zones by curtains, nevertheless, drying medium .from the adjacent dying and -ordering zones does tend to leak through :openings in the curtains for the conveyor into the cooling zone thereby upsetting temperature and humidity conditions in all three zones.

The present invention provides a solution to this problem by providing pressure control means for selectively regulating the pressure in the cooling zone and by providing pressure sensing means in the cooling zone and at least in one of the other zones for sensing pressure differences in the zones, the pressure sensing means being operatively connected to the pressure control means to effect actuation thereof to change pressure conditions in the cooling zone if pressure unbalance exists. By this arrangement, leakage between the zones is obviated and thus the treating conditions in all three zones may be controlled more accurately with the result that the nal condition of the treated material may be controlled accurately.

With the foregoing in mind, an object of the present invention is to provide a method and apparatus for treating material wherein the material is successively passed through drying, cooling and `ordering zones and wherein means is provided for maintaining uniform pressure in all of the zones so that the treating conditions in the various zones may be controlled accurately and whereby the nal condition of all of the material processed is substantially uniform.

Another object of the present invention is to provide a process for continuously treating materials to provide a linished product characterized by a predetermined, uniform moisture content and apparatus for carrying out the method which is of comparatively simple construction and may be manufactured economically.

These and other objects of the present invention and the various features and details of the operation of the apparatus and process and construction of the apparatus are hereinafter more fully set forth with reference to the accompanying drawings, in which:

FIGS. la and 1b are side elevational views of material treating apparatus constructed in accordance with the present invention;

FIG. 2 is an enlarged sectional View taken on line 2-2 of FIG. 1b;

FIG. 3 is an enlarged sectional view taken on line 3 3 of FIG. 2;

FIG. 4 is an enlarged sectional View take on line 4-4 of FIG. 1b; and

FIG. 5 is an enlarged Isectional view taken on line 5-5 of FIG. 1a.

Referring now to the drawings and particularly to FIGS. la and 1b thereof, there is illustrated a material treating apparatus 10 embodying means in accordance with the present invention for accurately controlling the nal condition of material processed therein. The apparatus 10 includes an elongated, generally enclosed housing 12 which in the present instance is divided by transversely extending, longitudinally spaced curtains or partitions P into treating zones, including a drying zone Zd, a cooling zone ZC, and an ordering zone Z0. In the illustrated embodiment, the drying zone Zd and ordering zone Z0 are further subdivided by curtains or partitions C.

A conventional conveyor 14 is mounted lengthwise of the dryer and actuatable by drive means for movement in an endless path to convey material to be processed through the various zones of the apparatus. The partitions P and C have elongated openings O therein to accommodate the conveyor 14. Conventional feed means F is provided adjacent the entrance end of the housing 12 to supply and deposit material to be processed on the upper run of the conveyor 14 for transport through the various treating zones.

Material deposited on the upper run of the conveyor 14 at the entrance end of the housing 12 is irst conveyed through the drying zone Zd where the material is subjected to a circulated heated treating medium to dry the material to a very low moisture content. To this end, a plurality of motor operated fans spaced Ialong the length of the apparatus in the drying zone Zd is provided to circulate drying medium. In the Ipresent instance, a bank of fans 20a is mounted below the upper run of the conveyor in one half of the drying zone Zd to circulate the drying medium upwardly through the material on the conveyor, and a bank o-f fans 20b is mounted above the upper run to circulate air downwardly through the bed of material in the other half of the drying zone Zd (see FIG. la). Conditioning means is provided for selectively controlling the condition of the drying medium circulated comprising in the present instance a plurality of heating coils 22 in the path of flow of the drying medium and inlet and outlet conduits 24 and 26 for circulating a heating medium such as steam therethrough, the inlet conduit having valve means 28 for selectively controlling the rate of steam ow through the heating coils 22.

After passage through the drying zone Zd, the material lis conveyed on the conveyor through the cooling about 700 grains per pound of dry air.

zone Zc where a cooled treating medium is circulated through the material to lowe-r the temperature of the material and place it in proper condition for ordering. In the present instance, the cooling medium circulating means comprises two identical units 29, each unit including an intake fan 30, mounted interiorly of the housing adjacent one end of an intake duct 32 which at its other end is open to the atmosphere, the intake fan 30 operating to draw fresh air from the atmosphere and expel the air over the material as shown in FIG. 2. Each circulating unit 29 further includes an exhaust fan 34 which draws the cooling medium through the material and discharges the air through an exhaust duct 36 which is also open at its outer free end to the atmosphere. In the present instance, the intake and exhaust fans 30 and 34 of each circulating unit 29 is mounted .in tandem on a common shaft 40 which in turn is driven from a source of power such as a motor 42 lconnected to the shaft 40 by a belt transmission 44.

The condition of the treating medium circulated in the cooling zone Zc may be selectively varied by means of a series of pivotally mounted dampers 54 in the intake duct 32 and a series of pivotallymounted dampers 56 in a branch manifold 60 connecting the inlet duct and the exhaust duct 36. The dampers 54 are actuatable simultaneously through shaft 55 and the series of dampers 56 are actuatable simultaneously through shaft 57. The shafts S5 and 57 are connected by linkage means 61 whereby operation of a control unit 62 connected to the shaft 55 elfects movement of both series of dampers. In the present instance, the arrangement is such that closing of the dampers 54 a given increment through shaft 55, opens the dampers 56 the same increment as the dampers 54. Thus the amount of fresh air and the amount of circulated air may be selectively regulated. In lieu of or in addition to the dampers 54 and 56, heating or cooling means may be provided in the intake duct 32 to condition the treating .medium circulated through the cooling zone ZC.

After the material has been cooled in the cooling zone Zc, the conveyor 14 transports the material through the ordering zone Zo where moisture is added to the material by a series of spray units or atomizers 70. Water or steam is delivered to the spray units through an inlet conduit 74 having valve control 76 for controlling the amount of water or steam owing to the spray units.

Consider now the treating conditions in the apparatus described for the treatment of a material such as tobacco wherein the initial moisture content of the material is 20 percent WWB [wet weight basis] and the desired nal condition of the material is 12 percentr CDB [commercial dry basis]. The temperature of the treating medium circulated upwardly in the first halt` of the drying lzone Zd is maintained at about 250 F. and the temperat'ure in the second half of the drying zone Zd wherein Vthe treating medium is circulated downwardly through 'the mate-rial is maintained at 220 F. The relative hu- Inidity of the treating medium in the drying zone Zd is The temperature of the treating medium in the cooling Zone Zn is maintained at about 80 F. and the relative humidity thereof 'is about 70 grains per pound of dry air. In the ordering zone Zo, the temperature of the treating medium circulated downwardly through the material is about 140 'F. and the temperature of the treating medium in the other half of the ordering zone Zo adjacent the delivery Vend is about 130 F. The relative humidity of the treating medium in the ordering zone Zo is about 80 grains per pound of dry air. Under these conditions it has been found in prior apparatus not employing the pressure control means of the present invention, that the pressure in the drying zone Zd at a point adjacent the cooling zone Zc is about +.25 inch of water [gauge] above the conveyor and about .15 inch of water [gauge] below the conveyor and that in the cooling zone Zc the 'processing a batch of material such .as tobacco.

pressure above the conveyor is about -|-.05 inch of water [gauge] 4and about l-.30 inch of water [gauge] below the conveyor. Further it has been found that in the section of the ordering zone Zo adjacent the cooling zone Zc the pressure is about -l-.20 inch of water [gauge] above the conveyor and about .05 inch of water [gauge] below the conveyor. Thus, due to the pressure differences in the various zones, it has been found that leakage between the zones does exist which makes it difficult to control the nal conditions of the material being treated.

In accordance with the present invention, means 1s provided for maintaining substantially uniform pressure conditions in the various zones of the apparatus to eliminate leakage between the zones whereby treating conditions in the various zones may be controlled more pre-cisely and in turn the inal condition of the material being processed may be controlled more closely. To this end, pressure control means is provided for varying selectively the pressure in at least one of the treating zones, in the present instance, the cooling zone ZC, in response to variations in pressure in pressure in the zones sensed by the sensing means.

It is noted that the pressures in the drying zone Zd and the ordering zone Zo are usually about the same. Accordingly in the present instance, the pressure control means for each of the circulating units 29 comprises a pair of blast gates G1 and Ge slideably mounted in the intake and exhaust ducts respectively and the sensing means comprises a U-tube manometer having one tap 92 over the conveyor in the drying zone Zd for sensing pressure in the drying zone Zd and another tap 94 over the conveyor in the cooling zone Zc for sensing the pressure in the cooling zone ZO. The taps 92 and 94 are connected through lines 93 and 95 to a control device '96 as shown in FIG. 4 which in turn is connected to actuating mechanisms M and N for blast gates G1 and Ge of each 'circulating uni-t. The cont-rol device 96 is conventional and maybe of the type manufactured and sold by The Foxboro Company, for example, the Foxboro M/4lA controller. By this arrangement, if vthe pressures sensed in the drying zone Zd and cooling zone Z,3 by the taps 92 and 94 are not substantially equal, the control device 96 is signalled to effect actuation of the blast gates Gi and Ge through their actuating mechanisms M and N to vary the pressure in the cooling zone until the pressure therein and in the other zones balances. 'More specifically, if the pressure in the cooling zone Zc is, for example, lower than in the adjacent drying zone Zd, the taps 92 and 94 Aregister the out of balance and the control device 96 is signalled to effect ,actuation ofthe gates G1 and Ge to raise the pressure in the cooling zone. The pressure in the cooling zone may be raised by opening the blast gate Gi in the air intake duct 32 or if this is .already opened, by closing the blast gate Ge in the exhaust duct 36 until the pressures fin the zones balance. The control device 96 may be arranged to actuate the dampers simultaneously until the taps 92 and '94 balance out at zero pressure differential.

Considering now the operation of the apparatus when The conveyor speed' and feed means are set relative to one another to deposit a layer of tobacco of a given thickness on the conveyor and the temperature and rate of circulation of the drying medium are set in the drying zone Zd to dry the material to a given predetermined moisture content. Additionally, the dampers 54 and 56 are set through the control unit `62 to condition the cooling medium for removal of a predetermined amount of heat from the 'tobacco in the cooling zone ZC. It is noted that if desired,

heating or cooling means may be provided in the inlet Ymanifold `to selectively heat or cool the air drawn in through the intake duct 32 depending on the temperature and condition of the outside air from which the air supply is drawn. Lastly, the spray units 70 .are set to eifect addition of a predetermined controlled amount of moisture to the material in the ordering Zone Z0.

If during processing of the material, the pressure in the cooling zone Zc drops below that in the drying and ordering zones the manometer registers the unbalance of pressures and signals the control device -96 to efrect actuation of the blast gates to raise the pressure in the cooling zone. To this end, the control device 96 effects opening of the blast gate G1 in the air intake duct 32 and/or closes the blast gate Ge in the exhaust duct 36 until taps 92 and 94 of the manometer balance out at zero pressure dilerential, On the other hand, if the pressure in the cooling zone Zc is greater than in the adjacent zones, the control device 96 on signal from the manometer actuates the blast gates Gi and Ge in a manner to lower the pressure in the cooling zone ZC. Of course, if the pressures in the zones balance, the manometer does not signal the control device 96 and no adjustment of theV blast gates is effected. If during processing of the material, it becomes desirable or necessary to change the condition of the air circulated in the cooling `zone Zc by adjusting the dampers 54 and 56, and 'if this adjustment affects the pressure in the cooling zone ZC, it is readily apparent that the manometer senses the pressure change and effects actuation of the blast gates through the control device 96 to compensate for the pressure dierential.

In view of the foregoing, it may be seen that the present invention provides a `relatively simple means for controlling pressure in the various sections of a material treating apparatus, whereby the conditions in the various sections may be controlled more precisely and the final conditions of the material being processed may be controlled more accurately.

While a particular embodiment ofthe present invention has been illustrated and described herein, it is not intended to limit the invention and changes and modications may be made therein within the scope of the following claims.

We claim:

1. A method of treating material consisting of the steps of subjecting the material to a gaseous treatment medium in at least two substantially enclosed treatment zones which are Iin limited free fluid communication, controlling the condition of the gaseous treating medium in each of said zones to provide a processed material having a predetermined condition, sensing the gaseous pressure in said treatment zones and varying the gaseous pressure in at least one of said treatment zones in response to pressure variations sensed between said zones thereby to substantially balance the gaseous pressure in said zones and minimize inow of gaseous medium between said zones.

2. A method of treating material consisting of the steps of conveying material along a predetermined path through at least two substantially enclosed zones which are n limited free uid communication, controlling the condition of a gaseous treating medium in each of said zones to provide processed material having a predetermined condition, sensing the gaseous pressure in said zones and varying the gaseous pressure in at least one of said zones in response to variations in gaseous pressure sensed between said zones thereby to substantially balance the pressure in said zones and minimize inow of gaseous medium between said zones.

3. A method of continuously treating material consisting of the steps of conveying material along a predetermined path through at least rst and second substantially enclosed treatment zones which are in limited free fluid communication, controlling the treating conditions in each said zones by means including circulating a heated gaseous drying medium through the material in said first treatment zone and circulating a cooled gaseous medium through the material in said second treatment zone, sensing the gaseous pressure in said first and second treatment zones and varying the gaseous pressure in at least one of said zones in response to variations in gaseous pressure sensed between said irst and second treatment zones thereby to substantially balance the gaseous pressure in said zones and minimize inflow of gaseous medium between said zones.

4. A method of treating material to process it to a desired condition consisting of the steps of heating the material in a heating zone by circulating a heated treating gaseous medium therethrough, cooling the heated material in a cooling zone by circulating a cooled gaseous treating medium therethrough, adding moisture to the cooled material in an ordering zone, said zones being substantially enclosed and in limited free Huid communication, sensing the gaseous pressure in at least two of said zones including the cooling zone and selectively varying the gaseous pressure in at least one of said two zones in response to variations in gaseous pressure in said zones sensed by said sensing means thereby to substantially balance the gaseous pressure in said zones and minimize inflow of gaseous medium between said zones.

5. A method of treating material consisting of the steps of conveying the material along a predetermined path successively through a drying zone, a cooling zone and an ordering zone, said zones being substantially enclosed and in limited free fluid communication, circulating a heated gaseous treating medium through the material in the drying zone to heat the material to dry the same to a given temperature, circulating a cooled gaseous treating medium through the material in the cooling zone to lower the temperature of the material therein, moisturizing the material in the ordering zone, maintaining the gaseous pressure in said drying andl ordering zones approximately equal, sensing the gaseous pressure in at least said drying zone and said cooling zone and selectively varying the gaseous pressure at least in said cooling zone in response to variations in gaseous pressures sensed between said drying zone and cooling zone thereby to substantially balance the gaseous pressure in said drying, cooling and ordering zones and minimize inflow of gaseous medium between said zones.

References Cited by the Examiner UNITED STATES PATENTS 540,271 6/1895 Proctor 131-136 585,759 7/1897 Hysore 131-136 629,368 7/ 1899 Hysore 131-136 1,999,469 4/1935 Molins 131-136 2,109,409 2/ 1938 Bogaty 131-136 2,151,947 3/ 1939 Touton 131-140 2,232,813 2/ 1941 Toutou 131--140 2,708,441 5/ 1955 Viglione 131--140 FRANCIS R. CHAPPELL, Examiner.

ABRAHAM G. STONE, Primary Examiner. 

1. A METHOD OF TREATING MATERIAL CONSISTING OF THE STEPS OF SUBJECTING THE MATERIAL TO A GASEOUS TREATMENT MEDIUM IN AT LEAST TWO SUBSTANTIALLY ENCLOSED TREATMENT ZONES WHICH ARE IN LIMITED FREE FLUID COMMUNICATION, CONTROLLING THE CONDITION OF THE GASEOUS TREATING MEDIUM IN EACH OF SAID ZONES TO PROVIDE A PROCESSED MATERIAL HAVING A PREDETERMINED CONDITION, SENSING THE GASEOUS PRESSURE IN SAID TREATMENT ZONES AND VARYING THE GASEOUS PRESSURE IN AT LEAST ONE OF SAID TREATMENT ZONES IN RESPONSE TO PRESSURE VARIATIONS SENSED BETWEEN SAID ZONES THEREBY TO SUBSTANTIALLY BALANCE THE GASEOUS PRESSURE IN SAID ZONES AND MINIMIZE INFLOW OF GASEOUS MEDIUM BETWEEN SAID ZONES. 